FS Canis Majoris variable

An FS Canis Majoris variable is a type of eruptive variable star. The class of variable stars are named after its prototype, FS Canis Majoris. They are somewhat poorly understood, most likely binary star systems in which mass exchange is ongoing or has recently happened, and most likely consist of at least one B-type main-sequence stars in a dust envelope. They undergo irregular light variations over long periods of time, with magnitude variation of approximately 2 magnitudes. The hydrogen emission lines from these stars are much stronger than in normal Be stars, and certain forbidden lines are present in the spectrum as well.